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29 records found
1.
Obst, B., R. Nast, et al. (2005). YBCO Coated Conductor Applications – A Texture Problem. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
YBa2Cu3O7-δ ("YBCO") is a high-temperature ceramic superconductor. Due to its complex layered structure, a strong biaxial texture of the YBCO grains is necessary to achieve technically relevant currents. In this paper, we describe the development of flexible metallic tapes with strong cube texture, providing a lattice-matched template for buffer and YBCO coatings in proper orientation. Texture analysis was performed using electron backscatter diffraction (EBSD).
2.
Ocelik, V. (2001). "EBSP study of reaction zone in SiC/Al metal matrix composite prepared by laser melt injection." Journal of Materials Science 36(20): 4845-4849.
The reaction zone in SiC/Al metal matrix composite layer prepared by Laser Melt Injection process is studied by Electron Back-Scatter Diffraction. Special attention is dedicated to the sample preparation process and also to the automatic indexing procedure when patterns of back-scattered electrons are evaluated during the surface scanning by electron beam. The orientation relationship between ceramic particles and phase formed in the reaction zone was observed by both transmission electron microscopy and by EBSD.
3.
Oertel, C. G., R. Tamm, et al. (2005). "Anomalous creep behaviour of aluminium high current joint materials." Crystal Research and Technology 40(1-2): 83-89.
During creep deformation the technical aluminium alloys EN AW-1350 (Al99.5) and EN AW-6060 (AlMgSiO.5) under certain conditions of stress and temperature show deformation thrusts of several millimetres, indicating discontinuous dynamic recrystallization. To study this anomalous creep behaviour in more detail the alloys were characterized by global and local texture measurements using neutron and electron backscatter diffraction (EBSD), respectively. In the case of AlMgSiO.5 the main global texture component of the undeformed sample is the cube component. During deformation and dynamic recrystallization a Goss component develops. The grain size slightly decreases with dynamic recrystallization. The normal creep behaviour is characterized by a Norton exponent of 3.8 and an activation energy of 0.5 eV. These parameters indicate that the strain rate controlling process is dislocation creep.
4.
Ogasawara, K., N. Sakai, et al. (2003). "Subgrain structures and superconductivity in RE–Ba–Cu–O bulk superconductors." Physica C 386: 225-230.
We have studied the microstructures of subgrains in large single-domain RE–Ba–Cu–O (RE = Y, Nd, Sm) bulk superconductors through microscopic observation and microarea X-ray pole figure analyses. The misorientation angle of subgrains increases as the crystal growth proceeds, and thus more crystal defects such as dislocations are seen at the later stage of the growth. Electron backscatter diffraction technique was successfully utilized for characterizing the subgrain boundaries. Electric and magnetic measurements for several samples containing different subgrain geometries have been performed. The results of I–V and resistivity measurements indicated that subgrains act as weak-links especially in a high magnetic field region.
5.
Oh, J. H., K. H. Kim, et al. (2006). "Growth of (100)-oriented polycrystalline Si film by Ni-mediated crystallization of thin amorphous silicon." Journal of the Electrochemical Society 153 (1): G12-15.
We studied the Ni-mediated crystallization of amorphous silicon (a-Si) as a function of its thickness. It was found that the orientation of the poly-Si changed from Ý110¨ to Ý001¨ when its thickness reduced down to 16 nm. This was confirmed by the analysis of electron backscattered diffraction pattern. The growth of (100)-oriented poly-Si is due to the predominant formation of Ý001¨ NiSi2 nuclei in a thin a-Si network because of its smaller crystalline size compared to that of Ý110¨ nuclei.
6.
Oh, S. T., K. K. Park, et al. (2002). Transformation Behavior of Retained Austenite in Hydroformed TRIP Steel. ICOTOM 13, Seoul, Korea, Trans Tech Publications Inc.
Tube hydroforming process as an optimum process for manufacturing structural parts of automotive and TRIP steel as a material of best strength-ductility balance have drawn increasing attention in the automotive industry. Employment of the TRIP phenomenon to produce steels with higher strength without loss of formability has been the subject of many recent investigations. To evaluate the stability of retained austenite, average volume fraction and micro-texture evolution under the various deformation mode, in-situ and ex-situ uniaxial tensile test and hydroforming test were performed and analyzed by EBSD. Granular type austenite was more rapidly transformed to martensite than film type does. The austenite of bended (for tube making) or hydroformed sample is more unstable than that of uniaxial mode, and thus more rapidly transformed to martensite. As deformation proceeds in uniaxial tension mode, the intensity of Goss and Brass component was gradually decreased.
7.
Oha, Y.-J., Y. S. Kima, et al. (2004). Characterization of Ultrafine Grain Structure in 5083 Al Alloy Made by Equal Channel Angular Pressing. Microscopy and Microanalysis 2004, Savannah, Georgia, USA, Cambridge University Press.
Equal-channel angular pressing(ECAP) is an attractive technique that can be used to impose large strain into materials and produce ultrafine grain structure, with corresponding improvements in mechanical properties such as high strength, high hardness and low temperature superplasticity. Recently, several researchers have investigated the effectiveness of the different repetitive processing routes and processing temperature of ECAP1-4. But a limited number of studies have been focused on the evolution of microstructure during the process. The aim of the current study is to present the changes in grain boundary property, microtexture and dislocation substructure during successive ECA pressings in 5083 Al alloy.
8.
Oh-Ishi, K., A. M. Cuevas, et al. (2003). The influence of Friction Stir Processing on Microstructure and Properties of a Cast Nickel Aluminum Bronze Material. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
Cast nickel-aluminum bronze (NAB) is specified for many marine applications due to its excellent corrosion resistance. Improved mechanical properties may be attainable using friction stir processing (FSP) to achieve localalized microstructure modification in cast material, and convert an as-cast microstructure to a wrought condition in the absence of macroscopic shape change. In effect, FSP provodes a means of surface hardening of castings. The complex physical metallurgy of cast NAB material will be reviewed, and the effect of FSP on microstructure of an as-cast NAB material will be described.
9.
Oh-ishi, K., A. P. Zhilyaev, et al. (2005). "Effect of strain path on evolution of deformation bands during ECAP of pure aluminum." Materials Science and Engineering A 410-411: 183-187.
The influence of strain path during equal channel angular pressing (ECAP) has been evaluated in pure aluminum by orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The material was examined after four pressing operations by route BC in a 90° die, or eight pressing operations by route BC in a 135° die. The von Mises equivalent strains were essentially the same for these two ECAP procedures. The microtexture data indicate that the distortion during ECAP corresponds to a simple shear in a direction approximately parallel to die-channel exit and on a plane perpendicular to the flow plane. For both procedures, the OIM data reveal prominent meso-scale band-like features. Lattice orientations in each band correspond to a texture orientation but the particular combinations of orientations depend upon ECAP die angle. High-angle boundaries in the structure correspond to interfaces between the bands.
10.
Oka, F. and S.-I. Muramatsu (2003). Microstructural investigation of polycrystalline silicon thin films re-crystallized by laser-diode. Proceedings of 3rd World Conference on Photovoltaic Energy Conversion, Osaka, Japan, Arisumi Printing Inc.
We carried out the recrystallization of small-grain-size poly-Si films by means of irradiation with continuous wave (CW) laser diode light (GaAlAs: 840 nm) scanning. The CW laser light produced by the laser diode induced lateral crystallization and yielded polycrystalline silicon with grains longer than 100 µm and with widths of up to 20 µm. Electron backscattered diffraction measurement (EBSD) was performed to analyze the crystalline structures, including grain shape, size, and orientation. Our measurements revealed that the orientations of the poly-Si films were textured. The mean grain area was over 1000 µm2.
11.
Okamoto, K., S. Inoue, et al. (2005). "Characteristics of single-crystal AlN films grown on ferromagnetic metal substrates." Physica Status Solidi A 202(14): R149-151.
We have demonstrated the first single-crystal growth of AlN films on Fe substrates using pulsed laser deposition and investigated their structural properties. Stepped and terraced surfaces of the Fe(110) substrates have been achieved by UHV annealing. Although a low quality AlN film, with randomly oriented polycrystalline grains, grows at a substrate temperature of 510°C, a single-crystal AlN film is achieved by lowering the growth temperature down to 430°C. The distributions of crystal orientations in the tilt and the twist directions for a AlN film measured by electron backscattered diffraction (EBSD) are 0.26 degrees and 0.58 degrees, respectively. Neither 30 degrees rotational domains nor cubic phase domains exist in the AlN films. We have also found that the intermixing reactions between AlN and the Fe substrates arc fully suppressed and the heterointerface is atomically abrupt. These results indicate that low temperature PLD growth technique allows us to grow single-crystal AlN on ferromagnetic substrates with an atomically abrupt interface.
12.
Oliveira, T. R. and F. Montheillet (2004). Effect of Niobium and Titanium on the Dynamic Recrystallization during Hot Deformation of Stabilized Ferritic Stainless Steels. Second Joint International Conference on Recrystallization and Grain Growth, ReX & GG2, SF2M, Annecy, France, Trans Tech Publications Ltd.
The study was carried out to understand the mechanisms occurring during dynamic recrystallization of hot deformed 11% chromium stabilized ferritic stainless steels and to compare the behaviour induced by various types of stabilization. It was observed that continuous dynamic recrystallization (CDRX) operates in all materials starting at the onset of straining. Niobium has a more pronounced influence on hardening than titanium during hot deformation, which is due to solid solution strengthening and also to the reduction or stopping of grain boundary migration by solute drag effect. The D2 component, {112}<111>, was found as the major texture component at the steady state for the torsion tests carried along the negative shear direction. It was likely to be formed by the combination of straining and growth of the grains exhibiting both low stored energy and low rotation rate of the crystallographic axes.
13.
Oliveira, T. R. and F. Montheillet (2005). Texture Evolution during Direct and Reversed Hot Torsion Tests of Stabilized Ferritic Stainless Steels. Textures of Materials - ICOTOM 14, Leuven, Belgium, Trans Tech Publications.
The study was carried out to understand the mechanisms occurring during the direct (negative shear direction) and reversed (positive shear direction) hot torsion of 11% chromium stabilized ferritic stainless steels. The behaviours induced by various types of stabilization, i.e., when either niobium, or titanium, or both niobium and titanium are used were compared. It was observed that continuous dynamic recrystallization (CDRX) operates in all materials starting at the onset of straining. Niobium has a more pronounced influence on hardening than titanium during hot deformation, which is due to solid solution strengthening and also to the reduction or stopping of grain boundary migration by solute drag effect. The D2 component, {112} <111>, was the major texture component at the steady state for the torsion tests carried along the negative shear direction. It was likely to be formed by a combination of strain and the growth of grains exhibiting both low stored energy and low rotation rate of the crystallographic axes. After reversion of the shear direction, i.e. during positive shear, the above major texture component is gradually changed into the D1 component, {112} < 111 >. Using the CMTP method (Continuum Mechanics of Textured Polycrystals), the stress evolution is explained by the volume fraction changes of each component at various strains, associated with their respective Taylor factors. Such simplified approach leads to a good agreement with experimental results.
14.
ONeill, W., M. Gill, et al. (2005). Analysis of femtosecond (775nm) and nanosecond (355nm) micromachined Ni surfaces using electron backscatter diffraction (EBSD). Photon Processing in Microelectronics and Photonics IV, San Jose, California, USA.
Advances in laser micromachining have resulted in considerable processing capabilities for the growing MEMS/MOMS applications currently being developed.
15.
Ono, Y., M. Hayakawa, et al. (2005). Visualization Observation Method Of Minute Diploid Material Structure Having Second Phase Particle. Publication Number- 05062173 JP
Document Type- A
Publication Date- 2005-03-10. Japan, National Institute For Materials Science. G01N023225; G01N00128; G01N00132; G01N023203.
PROBLEM TO BE SOLVED: To visualize the structure of a minute diploid material having a second phase particle in a bulk state without thinning a sample without being affected by the second phase particle. SOLUTION: The surface is allowed to have a difference of elevation of 50 nm or smaller, and a visualization observation is enabled by an SEM or EBSP measurement. COPYRIGHT: (C)2005,JPO&NCIPI
16.
Onoda, M., H. Wada, et al. (1997). "Crystal structures of low-temperature phases (phase II) of ionic conductors Ag7TaS6 and Ag7NbS6." Journal of Alloys and Compounds 262-263: 39-44.
The crystal structures of low-temperature forms of argyrodite-type ionic conductors, namely Ag7TaS6 II (between approx. 280 and 170 K) and Ag7NbS6 II (between approx. 280 and 140 K), have been analyzed and compared to each other using powder X-ray diffraction data. The crystal structure of Ag7TaS6 II could be described on the basis of a space group Pc with the lattice constant A = 7.453 Å, B = 7.403 Å, C = 12.806 Å and ß= 124.62°. In the Rietveld analysis of Ag7NbS6 II, a commensurately modulated structure approach was adopted to obtain a smooth convergence. The crystal data are expressed as a1 = 7.368 Å, a2 = 14.770 Å, a3 = 12.768 Å, Σ= (0.25, 0, 0), ß = 124.28° in a four-dimensional formalism with a superspace-group Pc (α, 1/2, γ, that is A = 29.47 Å, B = 14.770 Å, C = 12.768 Å, ß= 124.28° in a three-dimensional formalism with a space group C. In Ag7TaS6 II, three-sevenths of Ag ions are in the distorted S-S tetrahedrons and the residual four-sevenths are in the triangles shared by two tetrahedrons. On the other hand in the model of Ag7NbS6 II, most of a half of 28 independent Ag ions are in distorted tetrahedrons and most of the other half of Ag ions are in triangular faces shared by two tetrahedrons.
17.
Orlov, L. G., E. A. Golub, et al. (1984). "Identification of Grain-Boundary Dislocations by the Method of Theoretical Electron-Microscope Images." Industrial Laboratory-USSR 50(3): 237-243.
18.
Orsund, R., E. Nes, et al. (1989). "Local Lattice Curvature and Deformation Heterogeneities in Heavily Deformed Aluminum." Scripta Metallurgica 23(7): 1193-1198.
Recently, a method has been devised for measuring boundary orientations using backscattered Kikuchi diffraction (BKD, otherwise known as electron backscattering, (EBS). To illustrate its application, piece of recrystallised 99.0% purity nickel sheet of rectangular cross section and thickness 0.125mm was annealed in vacuum for 1 hour at 1050 degree C so that the resulting grain size was approximately 100 mu m. Geometrical parameters for 47 grain boundaries were measured. The work reported demonstrates that BKD can be efficiently used to measure both the misori
19.
Ortega, A. M., J. Tyber, et al. (2005). "Cast NiTi shape-memory alloys." Advanced Engineering Materials 7(6): 492-507.
20.
Orzol, J., C. A. Trepmann, et al. (2003). "Critical shear stress for mechanical twinning of jadeite—an experimental study." Tectonophysics 372: 135-145.
Coarse-grained natural jadeitite samples from Myanmar were experimentally deformed in a Griggs-type solid-medium apparatus at strain rates of 2&bul;10-5 and 5&bul;10-6 s-1 and temperatures of 900 and 1000 °C. The microfabrics of the deformed samples are investigated by scanning electron microscopy (SEM) using the electron backscatter diffraction (EBSD) technique. The critical shear stress for twinning in the (100) [001] system is derived from the orientation distribution of jadeite crystals with and without mechanical twins. The results indicate a homogeneous stress field within the sample and a critical shear stress of 150±25 MPa, which compares well to that determined by Kollé and Blacic [J. Geophys. Res. 87 (1982) 4019] for mechanical twinning of other clinopyroxenes. With the critical shear stress known, mechanical twinning of jadeite can be used as a paleopiezometer for high stress tectonic environments.
21.
Osa, T., H. Hosokawa, et al. (2000). Microstructural Dynamics during Elevated Temperature Deformation in A1-Mg Alloy. Thermec 2000, Las Vegas, Nevada, USA, Elsevier Science Ltd.
Grain boundary is an important microstructural element in polycrystalline materials, They can affect in a wide variety of phenomena which in turn affect the bulk properties of polycrystalline materials. Grain boundaries can play more significant roles in deformation and fracture as temperature increases, because grain boundary sliding migration, segregation, cavity forming and others intergranular phenomena initiate. It is well known that grain boundary sliding preferentially takes place at high angle boundaries during superplastic deformation so that misorientation between grain boundaries varies. It is important to understand the behavior of grain boundary characteristics during deformation. The studies of grain boundary characteristics with straining during superplastic flow have been investigated, however, the studies of grain boundary characteristics with straining in glide behavior have not been investigated yet. In this investigaton, grain boundary characteristics of superplastic behavior and glide behavior were compared in Al-Mg alloys.
22.
Ostafin, M., J. Pospiech, et al. (2004). Microstructure and texture in copper sheets after reverse and cross rolling. 2nd International Conference on Texture and Anisotropy of Polycrystals (ITAP 2), Metz, France, Balaban Publishers; Scitec Publications.
The objectives of this investigation are structural effects in electrolytic copper sheets which are caused by the change of the direction of rolling. Unidirectional, reverse as well as cross-rolling at 90 degrees respectively at 45 degrees to the precedent rolling direction have been applied down to final deformations as low as 80% reduction in thickness. Texture has been determined by ACOM (automated crystal orientation measurement, "automated EBSD ") in the SEM and by X-ray pole figure measurement. The main benefits of ACOM are a high spatial resolution which enables the investigation of texture gradients from the mid plane to the surface of the sheet, and the visualization of the microstructure by crystal orientation mapping. In addition to local texture, statistical distributions of misorientations across grain boundaries and of Sigma grain boundaries have been derived from the individual grain orientation data. The change of the path of plastic deformation induces a destabilization of the substructure which is formed during the primary step of unidirectional rolling. A distinct change of texture is found depending on the deformation process. In cross rolling, the beta fiber changes into the unstable beta 90 fiber which almost disappears with progressive deformation along the new rolling direction.
23.
Ostafin, M., J. Pospiech, et al. (2005). "The Evolution of Deformation Texture in Copper by Unidirectional and by Cross Rolling." Archives of Metallurgy and Materials 50(2): 409-415.
The change of the deformation path has a strong effect on the formation of cold-rolling texture. In particular, the texture stabilized during rolling becomes unstable and disintegrates when the rolling direction is changed in the last stitches from unidirectional or reverse rolling to pseudo-cross rolling by rotating the sample through an angle of 90DG or 45 deg about the normal direction. In addition to global texture, the microstructure is also specifically changed on a grain-size level. The change of the path of plastic deformation leads to a destabilization of the substructure which was formed during the primary step of rolling in one direction. In investigations on electrolytic copper distinct changes of texture and microstructure have been found depending on the deformation process. The orientation density function (ODF) shows that the reverse rolled starting sample of copper in this investigation contains only one component in the C={112} < 111 > position. By rotation about ND through 90 deg or 45 deg, the C component changes into the unstable C90={112} < 110 > or C45={112} < 914 > position, respectively, which almost disappears with progressive deformation. The effect of the mode of rolling on texture evolution has been studied in detail on a macroscopic scale by X-ray pole-figure measurement as well as on a grain-specific scale by individual grain orientation mapping (ACOM, "Automated EBSD ") in the SEM. The statistical distributions of grain orientations (pole figures, ODF), misorientations across grain boundaries (MODF) and Sigma grain boundaries are considered.
24.
Ostberg, G. (2005). "Mechanisms of plastic deformation of cemented carbide and cermet cutting tools." Doktorsavhandlingar vid Chalmers Tekniska Hogskola(2273): 72.
The physical mechanisms acting during plastic deformation of cemented carbide and cermet cutting tools were analyzed. It was observed that plastic deformation occurred under high loads in combination with high temperatures. It was also observed that the high temperatures increase the solubility and diffusion in the binder phase. The results show that the grain boundary sliding occurs by short range diffusional creep in the grain boundary region. (Edited abstract)
25.
Osterle, W. (1984). "Influence of the Dislocation Density and the State of Precipitation on the Yield Properties of a Microalloyed Fine-Grained Structural-Steel." Archiv für das Eisenhüttenwesen 55(6): 271-276.
26.
Ostwaldt, D., J. R. Klepaczko, et al. (1997). "Compression Tests of Polycrystalline Alpha-Iron Up to High Strains over a Large Range of Strain Rates." Journal de Physique IV 7(C3): 385-390.
27.
Othon, M. A., L. N. Brewer, et al. (2002). Electron Back-Scattered Diffraciton Misorientation Mapping Applied to Stress Corrosion Cracking of Stainless Steels. Microscopy and Microanalysis 2002, Québec City, Québec, Canada, Cambridge University Press.
28.
Oudin, A., M. R. Barnett, et al. (2003). Grain Size Effect on Behavior and Microstructure of a Warm Deformed Ti-IF Steel. Thermec' 2003, Leganés, Madrid, Spain, Trans Tech Publications Ltd.
The effect of grain size on the deformation behavior in the ferrite region of a Titanium stabilized Interstitial Free steel was investigated by hot torsion. The initial work hardening regime is followed by a softening regime where a broad peak stress develops. The peak stress and the stress at final strain were relatively insensitive to grain size. However, at low values of the Zener-Holloman parameter, the strain to the peak stress was strongly dependent on the grain size. A series of microstructural parameters were examined to explain these observations
29.
Ouyang, F., A. Ray, et al. (1992). Slow-Scan CCD Observation of Backscattering Patterns in SEM. 50th Annual Meeting of the Electron Microscopy Society of America, San Francisco Press.
29 records found
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